Abstract
Suicide peaks in late spring and October are still seen in Finland among many countries. Weather factors have been suggested as explanations for these peaks, although with inconsistent results. Since the exact timing of these peaks varies each year, the length of daylight and changes in it seem inadequate as an explanation. We hypothesized that ambient temperature and the timing of thermal seasons might associate with suicide rate. Suicide rates from three areas across Finland (N = 10,802) were analyzed with Poisson regression in six different models against variables calculated from the local ambient daily temperature, diurnal temperature range, and the duration from the onset of thermal seasons. Separate models for men and women were constructed. The temperature change over 5 days associated with the suicide rate of men in Helsinki region, or in other words, the lower the suicide rate was, the higher the temperature decrease had been. For women, the results were more inconsistent. Our study is in line with some earlier studies which imply that impairment of thermoregulation might exist among suicide victims.
Highlights
In our earlier nationwide study from Finland, suicide rate correlated with monthly mean temperature along with global radiation [1], and in another Finnish study, the ambient temperature variation was shown to explain even 60 % of the annual suicide variance in extra-long time series from 1751 to 2008 in Finland [2]
Suicide rates from three areas across Finland (N = 10,802) were analyzed with Poisson regression in six different models against variables calculated from the local ambient daily temperature, diurnal temperature range, and the duration from the onset of thermal seasons
The temperature change over 5 days associated with the suicide rate of men in Helsinki region, or in other words, the lower the suicide rate was, the higher the temperature decrease had been
Summary
In our earlier nationwide study from Finland, suicide rate correlated with monthly mean temperature along with global radiation [1], and in another Finnish study, the ambient temperature variation was shown to explain even 60 % of the annual suicide variance in extra-long time series from 1751 to 2008 in Finland [2]. The analysis of long series of monthly data on suicide and weather in Switzerland concluded that the association between temperature and suicide is not due to warm temperatures but due to the lack of low temperatures, or in other words, it is not heat but the Environ Health Prev Med (2014) 19:286–294 lack of cold that contributes to this association [9]. Differences between local climates may influence acclimatization, i.e., the physiological as well as psychological adjustment of individuals into local climate changes, and thereby may explain the conflicting results to some extent [10]
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